Wahiawa Water Hardness & Quality Report (2026)
Water Hardness
4.5 grains per gallon
Source
groundwater
pH Level
7.7
neutral = 7.0
Lead
0.009 mg/L
✓ Below action level
TDS
260.4 mg/L
Est. Daily Cost
$0.21
energy & soap waste
Source: USGS Water Quality Portal · Updated 2026
0–60
mg/L
Soft
61–120
mg/L
Moderately Hard
121–180
mg/L
Hard
180+
mg/L
Very Hard
Appliance Damage Report
In Wahiawa, your appliances are currently losing 10% efficiency due to mineral buildup.
| Appliance | In Wahiawa | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 7 yrs | 8.5 yrs | -18% |
| Washing Machine | 10.7 yrs | 12 yrs | -11% |
| Water Heater | 12.5 yrs | 15 yrs | -17% |
Regional Water Comparison
How Wahiawa compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Wahiawa, Hawaii | 77.5 mg/L | 1.5 ppt | 🟡 Moderately Hard | groundwater |
| Schofield Barracks, Hawaii | 76.5 mg/L | 1.5 ppt | 🟡 Moderately Hard | groundwater |
| Mililani Mauka / Launani Valley, Hawaii | 35 mg/L | 0.9 ppt | 🟢 Soft | groundwater |
| Mililani Town, Hawaii | 67.5 mg/L | 1.3 ppt | 🟡 Moderately Hard | groundwater |
| Royal Kunia, Hawaii | 76.5 mg/L | 1.5 ppt | 🟡 Moderately Hard | groundwater |
National Benchmark
How Wahiawa compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Wahiawa | 77.5 mg/L | 🟡 Low |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Wahiawa's Water Unique?
Local geology and source profile
Wahiawa, Hawaii, in Honolulu County — a Honolulu County city adjacent to Mililani and Schofield Barracks in the central Leilehua Plateau of Oahu — receives its municipal water from the Honolulu Board of Water Supply (BWS), drawing from the Wahiawa Reservoir (Kaukonahua Stream) and central Oahu's Leilehua Plateau basal freshwater lens wells.
The soft 77.5 mg/L hardness and TDS of 260.4 mg/L reflect the central Oahu volcanic-aquifer supply. The Koolau and Waianae shield volcanoes (Pleistocene-Pliocene tholeiitic basalt and alkalic basalt — relatively insoluble mafic volcanic rock) produce an essentially soft basal freshwater lens. The somewhat elevated TDS (260 mg/L for soft water) likely reflects minor brackish water mixing at the basal freshwater-saltwater interface in the central Oahu lens, a common characteristic of island freshwater lens systems.
At 77.5 mg/L, Wahiawa's water is soft — essentially no scale forms, soap lathers abundantly, and appliances maintain good efficiency. Annual descaling is sufficient. The PFAS level of 1.5 ppt is very low — among the lowest for any US city, reflecting the relative isolation of the central Oahu watershed. Schofield Barracks (US Army — AFFF on the Leilehua Plateau) is a noted PFAS source in the Wahiawa watershed, but the basal lens dilution keeps levels low.
Geology & Source: Wahiawa in Honolulu County draws from the Honolulu Board of Water Supply on Wahiawa Reservoir and central Oahu wells (Leilehua Plateau) — the Oahu aquifer is developed in Pleistocene-Pliocene Koolau Basalt (tholeiitic shield volcano) and calcareous Pleistocene coastal limestone — Hawaii Honolulu County Koolau basalt aquifer produces soft water at 77.5 mg/L with TDS 260.4 mg/L in this Honolulu County Hawaii city.